Carbon in the Sky (With Diamonds)

The carbon family includes coal, diamonds, and even some Nobel Prize winners: the soccer-ball-shaped molecules called buckyballs and the one-atom-thick sheets called graphene, which look like chicken wire and have promising possible uses in electronics, m

Carbon takes many shapes: coal, diamonds, and even some Nobel Prize winners such as buckyballs and graphene. Here on Earth, these materials have promising possible uses in electronics, medicine, and more. But increasingly, scientists are finding some of these allotropes, or different personas of carbon, scattered in space—or thinking about using them to get to space.

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Matthew Bailes

Diamond Planets

About 3900 light years away, a diamond planet that’s about the mass of Jupiter orbits a star called a pulsar—the collapsed core of a once-massive star.

By studying the pulsar’s wobble—how much it moves because of the tug of war with its planet—scientists led by Matthew Bailes at the Swinburne Centre for Astrophysics and Supercomputing in Melbourne, Australia, deduced the planet’s huge mass. And by noting the planet’s orbital time (about 2 hours) and close proximity to the pulsar (about 1.7 times the distance between Earth and the moon), the team estimated its density: at least 23 grams per cubic centimeter, or 7 times the density of jewelry diamonds. The team, which published their findings in Science in 2011, says the planet probably contains oxygen and carbon in a crystal form.

Still, extraterrestrial prospecting may be foolish: "The certainty over the structure and composition is far from 100 percent, just a very plausible explanation," Bailes says. Even if the planet is a crystalline orb, it is far from certain that it would glimmer like a terrestrial diamond, which is a cubic grid of carbon atoms.

Diamonds may be forever, but stars are certainly not. In fact, Bailes’s team believes the planet is actually the corpse of a white dwarf star that fused its fuel into a carbon core before the neighboring pulsar ripped off its coating, leaving the carbon behind. "We know of a lot of cases where there is a companion star stripping off material from a neighboring star," says Varun Bhalerao, a member of the team at Caltech, "but this scenario, of stripping a very dense white dwarf, is rather rare."

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NASA/JPL-Caltech

Space Balls

The buckyball is a cage of 60 carbon atoms aligned in pentagons and hexagons to make a design reminiscent of Disney’s Epcot Center. Given buckyballs’ ability to carry other molecules around in their hollow innards or to be festooned with other molecular chains, they promise potential use in science and tech applications such as drug delivery. Just this week a study came out in which mice fed olive oil laced with buckyballs lived far longer than those that ate the normal olive oil.

Researchers first imagined the buckyball in 1970 and created it in the lab in 1985. But despite its relatively recent discovery here on Earth, this conglomeration of carbon is common in space. In 2010, researchers announced they detected buckyballs 6500 light-years away. Jan Cami, an astronomer at the University of Western Ontario and researcher at the SETI Institute in Mountain View, Calif., led the team that used the Spitzer Space Telescope to look at their dust cloud home, a planetary nebula named Tc1. He says scientists can find these distant buckyballs by looking at how light from a nearby star changes frequency as it interacts with their jiggling bonds, and they may even use what they know about the buckyball’s behavior to learn about the other weird molecules in the dust cloud.

Buckyballs have turned out to be common in space. "When we discovered it, we weren’t quite sure if we were looking at something unique," Cami says. "Quite quickly after our paper came out, researchers found it in many other places." These places include planetary nebulae, lower radiation nebulae called proto-planetary nebulae, other galaxies, evolved stars, and carbon-rich stars called corona borealis stars. He estimates that, in objects like planetary nebulae, the particular molecule makes up about half of 1 percent of all of the carbon present.

Buckyballs have a big brother. It’s a rugby-shaped ball called C70, and like the buckyball, it is a member of a group of carbon molecules known as fullerenes, named after the futurist Buckminster Fuller.

In 2011, researchers announced the first detection of C70 outside our own galaxy—in the Magellanic Clouds, galaxies that orbit our own Milky Way. Letizia Stanghellini, a researcher at the National Optical Astronomy Observatory in Tucson, Ariz., and her team found buckyballs in the Magellanic Clouds the previous year, also using the Spitzer Space Telescope. And they say they also may have detected graphene, one-atom-thick sheets of carbon whose discoverers won the 2010 Nobel Prize in Physics. Here on Earth, researchers are now trying to tap graphene’s special properties to make a smorgasbord of nanotechnologies, including biosensors and transistors.

"Before 2010 all the fullerenes were looked for in many different environments," Stanghellini says. "It was not a surprise to have found them; it was a surprise not to have found them sooner." Carbon is one of the most abundant elements in space, she says. Graphite is seen in meteorites. Amorphous carbon, like that found in coal, is known to exist in interstellar space. "And then there are the more elusive molecules, C60, C70, and graphene," she says.

Part of the reason these molecules are so elusive is that you need specialized conditions to create them, Stanghellini says. In the lab, for example, they form in the absence of hydrogen atoms, which would otherwise bond with the carbon and hinder the formation of the complex carbon molecules. The exact circumstances of these molecules’ births in space are still up for debate, but Stanghellini and her team believes that the conception may have required shock waves powered by stellar winds.

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University of California - Santa Barbara

Lonsdaleite: When Death From the Sky Creates Diamonds

It came from outer space. Lonsdaleite, a hexagonal diamond, forms naturally in high-energy impacts, such as one from a comet or asteroid slamming into our planet. In 2012, a team of researchers including James Kennett, seen here, an earth science professor at University of California, Santa Barbara, found this kind of diamond here on Earth—the result, Kennett says, of one of these cosmic smash-ups.

In central Mexico’s Lake Cuitzeo, the scientists studied a well-known black layer of sediment that is widespread across North America. This layer, deposited on the planet about 12,900 years ago, contains lonsdaleite and several other types of nanodiamonds. They are the leftovers from a large cosmic strike that coincides with the beginning of a period of sharp cooling known as the Younger Dryas, and may have helped to hasten the melting and breakup of ice sheets that changed the planet’s ocean currents and led to the global cooling at that time.

"Lonsdaleite cannot be formed by any other process than the temperature and pressure that result from an extraterrestrial or cosmic impact with Earth," Kennett says. He explains that lonsdaleite formation requires these extreme conditions to warp the carbon atoms in cubic diamonds (such as those found at your local jeweler) into a hexagonal arrangement. Although this and several other kinds of diamonds are fairly common in this exotic black layer, their tiny size of 3 to 50 nanometers makes them a rather poor choice of gemstone for your sweetheart. But Kennett notes that these and other nanodiamonds like they found in the layer have a variety of industrial uses. For example, when mixed in paint, diamonds called n-diamonds and i-carbon, make for a sturdy, diamond-studded coating.

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Stephanie Getty, NASA Goddard

Carbon Nanotubes: Next Up in Space

Carbon nanotubes have yet to be found beyond our planet. But they could play a key role in humanity’s future in space.

Carbon nanotubes are just slightly harder than diamond, which is about five times harder than steel. But unlike diamond, these tubes are stretchy; they can extend by about 15 percent before they break, according to Steve Cronin, a professor of electrical engineering at the University of Southern California, who researches the mechanical properties of the special tubes. "If you look at their strength to weight ratio, it’s off the charts," he says.

As a result, carbon nanotubes are the material of choice for those hoping to realize the long-held engineering dream of building a space elevator. "Carbon nanotubes are your only way to get there," Cronin says, noting that other materials, like steel, would crumble under their own weight. But carbon nanotubes is hard to do well, and the lengthiest today are only centimeters long—a very short climb, indeed.

That’s just one idea. Engineers at NASA’s Goddard Space Flight Center in Greenbelt, Md., have announced a nanotube coating that can absorb 99 percent of a large range of light frequencies (seen here in ultra-close-up), from the infrared to the ultraviolet. NASA optical physicist John Hagopian, who led the team, says the key to the nanotubes, which are about 20 to 100 microns high, is that they transform light into heat that dissipates quickly. "Even though carbon is not a metal, in this form it acts like one," Hagopian says. When light strikes the tubes, the energy of the light particles is given to electrons shared between carbon atoms. These jostled electrons then transport the energy away as heat instead of reflecting it as light.

This property has much promise for tools like space telescopes where stray light makes precise detections difficult. The coating absorbs the extra light and keeps it from interfering with the light scientists want to measure. Thus, with carbon nanotubes aboard, space telescopes may have an even better chance of finding other space carbon brethren.

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